1. Field of the Invention
The present invention relates to coated substrates for medical purposes. The invention is particularly directed to medical devices or other substrates having lubricious coatings that are stored together where they can touch each other or are tortuously wrapped and folded upon themselves prior to use and are unfolded during use. In particular, one aspect of the present invention relates to lubriciously coated balloons that are folded and wrapped upon themselves for storage and are unwrapped and expanded to a size that is considerably greater than the stored size by the introduction of an expansion fluid into the balloon without having portions stick to each other and possibly removing the lubricious coating or tearing the substrate.
2. Description of the Prior Art
Medical balloon catheters are used surgically for insertion into blood vessels, urethra, or body conduits. Conventionally, such catheters are made of materials such as Nylon, Selar.RTM., polyethylene terephthalate (PET), polyethylene (PE) or similar materials. Also, such balloon catheters can be made of several layers with polyethylene terephthalate blended with polyethylene. Also they can be made with blends of polyethylene terephthalate and Hytrel. Hytrel is a randomized block co-polymer of polyethers and polyesters. Catheters have been rendered lubricious by coating them with a layer of silicone, glycerine or olive oil. Such coatings are not necessarily satisfactory in all cases because they tend to run off and lose the initial lubricity rather rapidly and they can also lack abrasion resistance. Hydrophilic coatings have also been disclosed such as polyvinyl pyrrolidone with polyurethane interpolymers or hydrophilic polymer blends of thermoplastic polyurethane and polyvinyl pyrrolidone.